Hearing instruments have over the later years been increasingly able to communicate with the surroundings, including communicating with remote controls, spouse microphones, other hearing instruments and lately also directly with smart phones and other external electronic devices.
Hearing instruments are very small and delicate devices and to fulfil the above requirements, the hearing instruments need to comprise many electronic and metallic components contained in a housing small enough to fit in the ear canal of a human or behind the outer ear. The many electronic and metallic components in combination with the small size of the hearing instrument housing impose high design constraints on the radio frequency antennas to be used in hearing instruments with wireless communication capabilities. As antennas get small compared to a transceiving wavelength of an electromagnetic field, a fundamental tradeoff between bandwidth and efficiency will arise.
Moreover, antennas, typically radio frequency antennas, in the hearing instruments have to be designed to achieve a satisfactory battery lifetime, good communication for all sizes and shapes of heads, ears and hair, in all environments and with as large frequency bandwidth as possible despite the space limitation and other design constraints imposed by the size of the hearing instrument.